Crate ndn_tlv

Provides abstractions for working with TLV-encoded data

Data that may appear as part of a TLV record should implement TlvEncode and TlvDecode. Types that represent a whole TLV record should implement Tlv in addition to TlvEncode and TlvDecode

At the core of the library are the three traits Tlv, TlvEncode, and TlvDecode.

Tlv should be implemented on types that represent a TLV record. In other words, types that, in their encoded form, start with a type and a length.

TlvEncode and TlvDecode are used for types that can be encoded/decoded and may appear in TLV records. All types implementing Tlv should also implement TlvEncode and TlvDecode.

To ease implementing these traits, a derive macro Tlv is made available. Simply derive it on an enum to automatically implement TlvEncode and TlvDecode. On structs, an attribute must be present to set the type ID of the TLV that this struct represents. Tlv will also be implemented on structs. Deriving TlvEncode and TlvDecode on structs without Tlv is not currently supported.

Please note that this library is under active development and the API is not stable.

Example

Here is a quick example of how the library may be used:

use bytes::{Buf, BufMut, Bytes, BytesMut};
use ndn_tlv::{Tlv, TlvEncode, TlvDecode, Result, VarNum, TlvError};

#[derive(Debug, Tlv, PartialEq)]
#[tlv(8)]
struct GenericNameComponent {
    name: Bytes,
}

#[derive(Debug, Tlv, PartialEq)]
#[tlv(1)]
struct ImplicitSha256DigestComponent {
    name: Bytes,
}

#[derive(Debug, Tlv, PartialEq)]
enum NameComponent {
    GenericNameComponent(GenericNameComponent),
    ImplicitSha256DigestComponent(ImplicitSha256DigestComponent),
}

#[derive(Debug, Tlv, PartialEq)]
#[tlv(7)]
struct Name {
    components: Vec<NameComponent>,
}

fn main() {
    let name = Name {
        components: vec![
            NameComponent::GenericNameComponent(GenericNameComponent {
                name: Bytes::from(&b"hello"[..])
            }),
            NameComponent::GenericNameComponent(GenericNameComponent {
                name: Bytes::from(&b"world"[..])
            }),
        ]
    };

    let data = name.encode();
    assert_eq!(data, &[
            7, 14, 8, 5, b'h', b'e', b'l', b'l', b'o',
                   8, 5, b'w', b'o', b'r', b'l', b'd'
        ][..]);
    let decoded = Name::decode(&mut data.clone()).unwrap();
    assert_eq!(decoded, name);
}

Re-exports

• pub use ::bytes;

Structs

• GenericTlv
  A generic TLV record whose type is only known at runtime
• VarNum
  A variable-length number as used by TLV encoded values

Enums

• NonNegativeInteger
  A non-negative integer, not encoded using VarNum
• TlvError
  Common error enum for library functions

Traits

• Tlv
  A TLV record
• TlvDecode
  Decode data in TLV format
• TlvEncode
  Encode data in TLV format

Functions

• find_tlv
  Advance bytes until a valid TLV record of type T is found
• tlv_critical
  Returns whether a TLV is “critical”
• tlv_typ_critical
  Returns whether a TLV with a given type typ is “critical”

Type Aliases

• Result
  Common result type for library functions

Derive Macros

• Tlv